what is castner-kellener process.......
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Answers
Answer:
CASTNER-KELLER CELL
Catner-Keller cell is a common cell consists of rectangular tank in which mercury flows along the bottom of the cell.
ELECTRON USED
Mercury as cathode and carbon as anode.
PROCESS
The brine solution also flows in the same direction. When electricity is passed, following reaction takes place at different electrodes.
NaCl ⇌ Na+ + Cl-
At Cathode
Na+ + e− → Na (amalgam)
At anode
Cl− →1/2 Cl2 + e−
The advantage of using Hg as a cathode is that the discharge potential of Na+ ions is less than that of H+. Na+ ions get discharged on mercury and sodium so deposited combines with mercury to form sodium amalgam flows out and treated with water to give sodium hydroxide and hydrogen gas.
2Na. amalgam + 2H2O → 2NaOH + 2Hg + H2
During electrolysis, hydrogen is evolved at cathode and chlorine is evolved at anode, which are the by product of this process. The mercury produced in last step is recycled.
Answer:
The apparatus shown is divided into two types of cells separated by slate walls. The first type, shown on the right and left of the diagram, uses an electrolyte of sodium chloride solution, a graphite anode (A), and a mercury cathode (M). The other type of cell, shown in the center of the diagram, uses an electrolyte of sodium hydroxide solution, a mercury anode (M), and an iron cathode (D). The mercury electrode is common between the two cells. This is achieved by having the walls separating the cells dip below the level of the electrolytes but still allow the mercury to flow beneath them.[7]
The reaction at anode (A) is:
Cl− →1/2 Cl2 + e−
The chlorine gas that results vents at the top of the outside cells where it is collected as a byproduct of the process. The reaction at the mercury cathode in the outer cells is
Na+ + e− → Na (amalgam)
The sodium metal formed by this reaction dissolves in the mercury to form an amalgam. The mercury conducts the current from the outside cells to the center cell. In addition, a rocking mechanism (B shown by fulcrum on the left and rotating eccentric on the right) agitates the mercury to transport the dissolved sodium metal from the outside cells to the center cell.
The anode reaction in the center cell takes place at the interface between the mercury and the sodium hydroxide solution.
2Na (amalgam) → 2Na+ + 2e−
Finally at the iron cathode (D) of the center cell the reaction is
2H2O + 2e− → 2OH− + H2
The net effect is that the concentration of sodium chloride in the outside cells decreases and the concentration of sodium hydroxide in the center cell increases. As the process continues, some sodium hydroxide solution is withdrawn from center cell as output product and is replaced with water. Sodium chloride is added to the outside cells to replace what has been electrolyzed